Complication is a business. Moving goods, money and people between Britain and the continent got harder, and a professional layer grew to handle it: customs brokerage, trade compliance, regulatory consulting, immigration and mobility services, cross-border legal practice, and a steady output of policy analysis. UK-EU is how that relationship is written in every document about it, and four characters with no hyphen is about as compact as the pair gets. The name reads correctly to everyone working in the field, which is the only audience that matters for it.